Huntington’s disease neurodegeneration occurs when the number of consecutive glutamines in the huntingtin exon-1 (HTTExon1) exceeds a pathological threshold of 35. The sequence homogeneity of HTTExon1 reduces the signal dispersion in NMR spectra, hampering its structural characterization. By simultaneously introducing three isotopically labeled glutamines in a site-specific manner in multiple concatenated samples, 18 glutamines of a pathogenic HTTExon1 with 36 glutamines were unambiguously assigned. Chemical shift analyses indicate the α-helical persistence in the homorepeat and the absence of an emerging toxic conformation around the pathological threshold. Using the same type of samples, the recognition mechanism of Hsc70 molecular chaperone has been investigated, indicating that it binds to the N17 region of HTTExon1, inducing the partial unfolding of the poly-Q. The proposed strategy facilitates high-resolution structural and functional studies in low-complexity regions.

当亨廷顿外显子 1 (HTTExon1) 中的连续谷氨酰胺数量超过病理学阈值 35 时，就会发生亨廷顿舞蹈病神经变性。HTTExon1 的序列同质性降低了 NMR 光谱中的信号分散，阻碍了其结构表征。通过在多个串联样品中以位点特异性方式同时引入三种同位素标记的谷氨酰胺，明确分配了致病性 HTTExon1 的 18 种谷氨酰胺和 36 种谷氨酰胺。化学位移分析表明 α-螺旋在同源重复序列中持续存在，并且在病理阈值周围没有新出现的毒性构象。使用相同类型的样品，研究了 Hsc70 分子伴侣的识别机制，表明它与 HTTExon1 的 N17 区域结合，诱导 poly-Q 的部分展开。拟议的策略有助于在低复杂性区域进行高分辨率结构和功能研究。